A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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4 views

paired subject design test of proportions

I am analyzing a performance data set and would like to compare across two different conditions. I have three subjects, which were tested over a number of trials. Each trial had a chance of being in ...
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11 views

About multiple testing and power analysis

Doing a power analysis for a single t-test is relatively simple. What if I have to do several tests? If I were to use the Bonferroni correction, I could just take the significance level as 0.05 ...
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1answer
21 views

Unequal sample size one way ANOVA

I want to compare the means of X between BMI groups, but have unequal sample sizes between my groups. ...
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1answer
56 views

What is not normal distribution?

I am running analyses for my dissertation and just got myself in a muddle. I am running descriptive stats to determine whether to use paired t-tests vs Wilcoxon signed rank tests. I've read that it ...
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0answers
14 views

Test if two means are significantly different in R [duplicate]

I would like to test if two means are significantly different from each other. I am using R and I do this: t.test(SampleA,SampleB) and I get output that looks ...
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40 views

Dissertation-results section

basically i am testing 2 species of pigs, 2 pigs of the same species in one enclosure and another 2 in a different enclosure, My aim is to see if alterations to feeding regimes have an effect on an ...
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1answer
16 views

Pre-post measurements with a control group

I am running a study looking at the effect of Vitamin C on muscle function. For my study design, I had 2 groups: A treatment (vit C) and a control (no treatment) group. Pre and post measurements were ...
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0answers
12 views

Performing t test, one-way ANOVA from mean and SD using SPSS

I have the following summarized data: Group 1: n=44, mean 12.1, SD 2.0 Group 2: n=56, mean 13.2, SD 2.5 Group 3: n=42, mean 12.7, SD 2.3 Is it possible to perform the t test comparing means of group ...
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1answer
34 views

Test if two gamma distributed populations are different

I have data from two populations of different sizes. Both have Gamma distributions with different shapes and scales (as estimated in r): fitdistr(x/10000, "gamma") #186 members shape 0.586219900 ...
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19 views

Comparing means between two groups if dependent variable is a percentage

I have data on recovery rates from several hospitals across the country. The recovery rates are in percentages. I want to compare the mean recovery rate between two groups of hospitals, one that uses ...
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17 views

Equivalent to Welch's t-test in GLS framework

How can Welch's t-test be expressed as a generalized least squares model? A standard independent samples t-test (where it is assumed that the samples being compared are drawn from populations with ...
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1answer
50 views

Size of Tukey's 1 Degree of Freedom Test

In Oehlert (p. 218) the following algorithm for computing Tukey's one degree of freedom test for non-additivity is suggested: Fit a preliminary model; this will usually be an additive model. ...
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1answer
58 views

simulate t-tests of mean differences

I would like to simulate t-tests of mean differences. I would like to simulate data based on 1) pre-specified (desired) mean difference between the variables and 2) desired t value 3) and p-value ...
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2answers
28 views

Should I use paired t-tests or ANOVA when comparing multiple variables from 2 tests?

I had 50 subjects perform two 30-minute cycling time trials on separate days. I would like to compare the means of several variables from each of the two tests: Cadence, Heart Rate, Power Output, and ...
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13 views

Concept of performing a t-test while controlling/adjusting for one or more variables? [duplicate]

Could someone please help me understand the concept of performing a t-test while controlling/adjusting for one or more variables? E.g.: Say I have a hypothetical data set, with the following ...
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1answer
19 views

Properly interpreting and presenting a differences in differences t-test in written and table forms

I have two separate groups of students. A control (n=23) and intervention (n=19) group. Both groups took a pre test measure (score of 0-100). I have done an independent t-test on the Post_minus_Pre ...
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1answer
23 views

Can I do a dependent t-test if pre & post were anonymous?

I am trying to analyze the following case study using SPSS. What I have done so far as part of my research is to conduct a case study to measure the affect the introduction of different technology ...
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26 views

Longitudinal pre-post test/follow up

I am an undergrad student trying to get my head around statistical analysis. Can someone help me to make sense of the best way to analyse my data? ANOVA, ANCOVA, t-tests....it is all a foreign ...
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1answer
54 views

Test for equality of lines, simple regression

I have two data sets with the same predictor and response and I want to obtain a p-value that they follow the same regression model $E(y)=ax+c$. Sample sizes are different. What test should I use? ...
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12 views

Formally stating hypotheses with two parts

I'm trying to state my hypotheses formally for my dissertation, but I'm getting my brain in a twist here. H0: (µ1- µ2) – (µ3- µ4) ≤ 0: The mean difference in response time between low load ...
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1answer
33 views

t-test, which version to use?

I have a very small data set, with two groups, 5 cases in each one. I ran the t-test, and got a p value of 0.049. The F test that SAS ran in addition gave a p value of 0.72. This is not a surprise, ...
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1answer
15 views

How should I present paired sample test results? [closed]

I conducted a paired sample t-test on pre and post questionnaire results. What should I be reporting?
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2answers
61 views

Calculate t-statistic step by step in R

Hello: I'm a faculty member teaching a stats class, and I'd like to show students how to calculate the t-statistic from an independent samples t-test (mostly) step-by-step. Using the code below, ...
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1answer
60 views

Effect of sample size in F-test?

Having worked hard to understand the t-test, I'm rapidly falling out of love with it. All that is required in the t-test to gain significance is increase sample size, which renders it close to ...
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5 views

Post-hoc test on 3 groups comparison

I have 3 groups each with 6 values. After performing acceptable levene test for Homogeneity of Variance, I performed Anova on my data. It was significant, and I started to perform post-hoc test. The ...
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36 views

Question about normality assumption of t-test

For t-tests, according to most texts there's an assumption that the population data is normally distributed. I don't see why that is. Doesn't a t-test only require that the sampling distribution of ...
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2answers
71 views

Help performing hypothesis tests automatically on a large data set in R

I have a data frame in R with 100 variables (columns) and 100 observations (rows). Each row is a patient; the columns are different variables such as gender, height, body-mass index, etc. I know that ...
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34 views

is it legitimate to t-test between statistics of a bootsrap?

say I have two samples $x_1$ and $x_2$ and a function which calculates a statistic out of each sample, denotes as $f(x)$. I would like to test the significance of the difference $f(x_1)-f(x_2)$. A ...
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2answers
32 views

Testing if distribution is similar between two groups

I have a variable young that is equal to 1 if a participant is less than 25 years old. I then have a list of of each ...
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22 views

Analyzing Proximity Pattern Data in Gorillas

I have a whole bunch of data about proximity patterns between 2 gorillas (distance in meters, taken during set time intervals). I'm interested in comparing the differences in proximity between the 2 ...
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23 views

Multiple t tests or an ANOVA?

I have low anxiety and high anxiety participants (21 in high anxiety and 20 In low). I measured anxiety and then categorised Pts according to this. They completed two memory tasks. In one memory ...
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1answer
84 views

How do you tell if you should use a one-tailed test or a two-tailed test in a t-test?

For example, how would you decide between which tailed test to do in the following experiment: Ethanol dilutions were made with different proportions and Daphnias were submerged in them to collect ...
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2answers
30 views

Cohen's d in non-significant results

I did several independend t-tests. Some of them are significant, some of them are not. Next, I computed Cohens $d$ for effect size. For significant results, Cohens $d$ feels intuitively reasonable ...
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1answer
19 views

Analyze multiple measurements per subject?

I have 2 subjects. I used to take a single measurement (20 samples) per subject and use a t-test to compare the means. Now I want to add more measurements. I'm going to have 5 measurements per ...
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1answer
20 views

Determine if there is a difference between two large vectors of different sizes of non-normal quantiative data in R

I have two vectors that are of unequal sizes. They contain quantitative data that does not form a normal distribution. I would like to see whether or not they are statistically different. Is there a ...
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38 views

Normality and homogeneity

I have performed certain statistical tests (ANOVA, DMRT, t-test, etc.) assuming my data is normal as well as with homogeneous variance. Now my paper is almost accepted in a reputed journal, reviewer ...
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1answer
69 views

Paired difference t-test vs independent two sample t-test to assess means difference

If I want to compare two sets of measurements, i.e., how much their means differ or how much the sets differ, I would say I have two options: Paired difference t-test: Calculate the differences to ...
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10 views

How many number of items should i include in my test?

I have designed two post test ,a recognition test and a production test.I have inserted 18 items in each test. As I sifted through articles , I 've read that we should include at least 30 items to get ...
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11 views

T-test degrees of freedom

I have just been creating a slide demonstrating a (central interval) confidence band plot using a Neyman construction for a simple standard normal distribution. I created a confidence band plot of ...
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0answers
52 views

Basic methods for detecting outliers

Let $X$ be a matrix of $n$ rows and $m$ columns. $n$ is the number of samples and $m$ is the number of gene expressions. Gene expressions are basically numerical continuous values. Assume we have a ...
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18 views

Can I compare three averages if no independent variable?

I am not used to this type of data, and am not experienced with statistics so am really getting hung up. This is an undergraduate research project. I have done a total fecal collection on 12 horses. ...
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1answer
16 views

What Statistical Test of Significance is Suited to Comparing Two Classes of Students on Volume of Access?

I'm an educator and I'm delving a little further into stats than I normally would to try to determine how effective a new teaching method is. I'd really appreciate some advice on the best approach to ...
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2answers
13 views

Methods for compiler benchmarking?

In computer science, statistical knowledge is quite low in general. You rarely see standard deviation in papers. Now I am trying to improve at least my skills, but I find myself utterly confused about ...
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1answer
26 views

One-tailed vs. two-tailed t-test and P level

In a two-tailed t-test for a P of 0.1 and a one-tailed test for a P of 0.05, is the t value to show significance the same? I understand that the two-tailed test is looking for significance at either ...
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1answer
23 views

How to compare two Bayesian networks?

I have two different datasets on which I've applied the same learning (K2) algorithm to learn a Bayesian network. I have the conditional probability table (CPT) of the class variable, for each of the ...
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36 views

Which is the best statistical test for assessing the quality of a prediction?

I have a function that I'm trying to modulate and I would like to have a statistical indicator that inform me how good / poor my prediction is. In the image below, I show the function (...
2
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1answer
28 views

Paired permuted t-tests?

I have a small dataset which are not normally distributed. I would like to perform a pairwise analysis of the differences in values between two groups. It has been suggested that I use permuted ...
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1answer
133 views

Significant t-test results accurate or random?

I've performed a bunch of independent t-tests looking for a relationship between 10 different variables in group A and 10 different variables in group B. There seems to be very few significant ...
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1answer
19 views

Comparison of mean values between two periods

An authority has decided to legislate on stricter rules regarding amortization. The previous legislation stated that a mortgage loan has to be amortized down to a degree of at least 75% of the price ...
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19 views

Multiple T-Test with Trended Data in R

I am having issue getting the p-values from a T-Test for a 'typical trended study'. The aggregated values for satisfaction by months are the following. ...